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Sky at a Glance | October 7th, 2011

Supernova 2011fe, which erupted in the galaxy M101 on August 24th, peaked at magnitude 9.9 in early to mid-September and was down to about magnitude 11.3 as of October 6th. It has also been turning ever deeper orange-red. Catch it right after dusk before it moves lower in the northwestern sky. For charts and other information see our article The M101 Supernova Shines On.

Friday, Oct. 7

Look high in the east this evening, far left of the Moon, for the Great Square of Pegasus, a signature star-sign of autumn. It's balancing on one corner. Your fist at arm's length probably just fits inside it.

Use this chart to locate Mira well to Jupiter's lower right.

S&T Illustration

Later in the evening, once Jupiter is well up in the east, use the chart at right to check on the red variable star Mira in Cetus. Mira is still in an unusually bright maximum at about magnitude 2.4, quite plain to the unaided eye despite the moonlight. Mira should start to fade this week. See our earlier article.

Saturday, Oct. 8

The Draconid (Giacobinid) meteor shower may have spasms of strong activity during good observing hours for Europe or possibly elsewhere. Various predictions put one or more outbursts between about 17:00 and 21:00 Universal Time (GMT). The shower's radiant is near the head of Draco, but the meteors themselves can flash into view anywhere in the sky. Unfortunately, the light of the waxing gibbous Moon will obscure all but the brightest meteors. See our article, A Mad Dash for the Draconids.

The bright eclipsing variable star Algol in Perseus should be in one of its periodic dimmings, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 7:49 p.m. EDT. Algol takes several additional hours to fade and to rebrighten.

For timetables of all of Jupiter's Red Spot transits and satellite events this month, see the October Sky & Telescope, page 54.

Monday, Oct. 10

Even as the stars begin to come out in twilight, Cassiopeia is already higher in the northeast now than the sinking Big Dipper is in the northwest. Cassiopeia's broad W pattern is currently standing on end.

Tuesday, Oct. 11

Full Moon (exact at 10:06 p.m. Eastern Daylight Time). The Moon is in dim Pisces, below the Great Square of Pegasus.

The bright Hunter's Moon passes Jupiter in the east after dark. Mira is the crook in the purple line just below the S in CETUS. The blue 10° scale is about the width of your fist held at arm's length.

Now that it's mid-October, Deneb has replaced Vega as the zenith star after nightfall (for skywatchers at mid-northern latitudes)  and, accordingly, Capricornus has replaced Sagittarius as the most notable constellation low in the south.

Saturday, Oct. 15

Once the waning gibbous Moon rises this evening, look for the Pleiades above it.

Want to become a better amateur astronomer? Learn your way around the constellations. They're the key to locating everything fainter and deeper to hunt with binoculars or a telescope.

For an easy-to-use constellation guide covering the whole evening sky, use the big monthly map in the center of each issue of Sky & Telescope, the essential magazine of astronomy. Or download our free Getting Started in Astronomy booklet (which only has bimonthly maps).

Sky Atlas 2000.0 (the color Deluxe Edition is shown here) plots 81,312 stars to magnitude 8.5. That includes most of the stars that you can see in a good finderscope, and typically one or two stars that will fall within a 50× telescope's field of view wherever you point. About 2,700 deep-sky objects to hunt are plotted among the stars.

Can a computerized telescope take their place? I don't think so  not for beginners, anyway, and especially not on mounts that are less than top-quality mechanically. As Terence Dickinson and Alan Dyer say in their Backyard Astronomer's Guide, "A full appreciation of the universe cannot come without developing the skills to find things in the sky and understanding how the sky works. This knowledge comes only by spending time under the stars with star maps in hand."

This Week's Planet Roundup

Mercury (about magnitude 0.7) is very deep in the sunset. For a real challenge, use binoculars or a telescope shortly after sundown if the air is very clear to see if you can pick up Mercury barely above the horizon to the lower right of Venus. Good luck.

Venus (magnitude 3.9) is just above the west-southwest horizon 15 or 20 minutes after sunset. Binoculars help. If you spot Venus, you'll be one of a small number to see it this early in its apparition  compared to the billions who will see it as the Evening Star blazing high in twilight in the coming months.

Mars (magnitude +1.3, in Cancer) rises around 1 or 2 a.m. daylight-saving time. By the beginning of dawn it's in good view high in the east, well below Castor and Pollux. Well to the upper right of Mars is Procyon. Off to Procyon's lower right shines bright Sirius. In a telescope, Mars is a tiny blob only 5 arcseconds wide.

Io and darker Callisto were just east of Jupiter when S&T's Sean Walker imaged the scene on the morning of September 19th. South is up. Note the reddish Oval BA, "Red Spot Junior," just past the central meridian in the South Temperate Belt.

S&T: Sean Walker

Jupiter (magnitude 2.9, in southern Aries) rises in the east-northeast during twilight and blazes brightly in the east to southeast all evening. Look above it for the stars of Aries and closer below it for the head of Cetus, rather dim. (And don't miss Mira, now unusually bright and plain to the naked eye, to the right of the head of Cetus. See our article Observe Mira, the Amazing Star.)

Jupiter shines highest in the south after midnight, making this the best time to examine it with a telescope. It's a big 49 arcseconds wide, essentially as big now as it will appear at its October 28th opposition. See our guide to observing Jupiter with a telescope.

Saturn is out of sight in conjunction behind the Sun.

Uranus (magnitude 5.7, in Pisces) and Neptune (magnitude 7.8, in Aquarius) are well placed in the south and southeast by mid- to late evening. Use our printable finder chart for both, or see the September Sky & Telescope, page 53.

All descriptions that relate to your horizon  including the words up, down, right, and left  are written for the world's mid-northern latitudes. Descriptions that also depend on longitude (mainly Moon positions) are for North America. Eastern Daylight Time (EDT) equals Universal Time (also known as UT, UTC, or GMT) minus 4 hours.

NEW BOOK: Sue French's DEEP-SKY WONDERS! This big, long-awaited observing guide by Sky & Telescope's Sue French is now available from Shop at Sky. Hefty and lavishly illustrated, it contains Sue’s 100 favorite sky tours (25 per season, with finder charts) from her 11 years of writing the Celestial Sampler and Deep-Sky Wonders columns for S&T. Don’t miss it!

About Alan MacRobert

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Our calendar combines gorgeous astrophotography and special sky scenes that illustrate the positions of the Moon and bright planets. It also highlights the important celestial events of every month, including solar and lunar eclipses, meteor showers, conjunctions, and occultations of bright stars by the Moon.